Abstract

Scirpus validus was grown hydroponically and exposed to the pharmaceuticals, carbamazepine and naproxen at concentrations of 0.5-2.0 mg L(-1) for an exposure duration of up to 21 d. By the end of experiment, carbamazepine elimination from the nutrient solution reached to 74%, while nearly complete removal (>98%) was observed for naproxen. Photodegradation and biodegradation played only minor roles for carbamazepine elimination, while naproxen showed a high potential for both photodegradation and biodegradation. Levels of carbamazepine ranged from 3.3 to19.0 μg g(-1) (fresh weight) in the roots and 0.3-0.7 μg g(-1) (fresh weight) in the shoots, while naproxen concentrations were 0.2-2.4 μg g(-1) (fresh weight) in the roots and 0.2-2.8 μg g(-1) (fresh weight) in the shoots. Bioaccumulation factors (BAFs) for carbamazepine ranged from 5.5 to 13.0 for roots and 0.3-1.0 for shoots, and uptake by S. validus accounted for up to 22% of the total mass loss of carbamazepine in the nutrient solutions. All BAFs for naproxen were less than 4.2 and plant uptake accounted for less than 5% of the total mass loss of naproxen, implying that plant uptake was not significant in naproxen elimination. The rather limited plant uptake of naproxen was not surprising despite the fact that its log K(ow) is close to the optimal range (1.8-3.1) for maximal potential for plant uptake. Apparently, for ionizable compounds such as naproxen, the effects of pK(a) and pH partitioning might be more important than lipophilicity.